How Sleeve-valve Engines Work

Harry R. Ricardo (later "Sir" Harry Ricardo), born in London in 1885, didn't wait until college to begin his engineering studies. He observed and absorbed at the knee of a local machinist as a young boy, and would go home from the machinist's shop to apply his new knowledge in building engines. He would later say:

"As a child, I was always fascinated by engines and mechanical motions generally, and above all, by the great mystery as to how such things were actually made...looking back, I think I learnt more of actual value from these early and very crude attempts at design and manufacture than from anything else" [source: University of Cambridge].

Ricardo, in his working engineer adulthood, was an incurable overachiever. In addition to tweaking the engines on tanks that helped break the stalemate of World War I, he led ground-breaking research into assigning octane ratings to different grades of fuel.

Perhaps his most notable contribution in the World War II years was his work on making the sleeve-valve engine better.

Ricardo theorized in the 1920s that a sleeve-valve airplane engine could generate greater horsepower than a comparable tappet-valved engine because it could generate a higher compression ratio.

It so turned out that by 1941, British aircraft including the mainstay Supermarine Spitfire fighter plane, were taking a pounding from Germany's superior Focke-Wulf Fw 190. The Fw 190s also launched ground attack raids on Allied installations with near-impunity, since nothing could catch them at low altitude after they dropped their bombs.

The sleeve valve-engined Hawker Typhoon, entering service in 1942, changed that. Propelled by a 2,180-horsepower Napier Sabre engine, the "Tiffy's" extra get-up-and-go meant it could not only shoot down quick Luftwaffe interlopers, but it could carry bombs as well. Later in the war, bomb- and rocket-equipped Typhoons would prove pivotal in supporting Allied ground forces as they tightened the noose on the Nazis and ended the war in Europe [source: Rickard].

Despite the sleeve-valve engine's exemplary military record, the writing was on the wall: jet engines would dominate commercial and military aviation from the postwar years forward.

The legacy of Knight, Ricardo and others would not completely go away -- engine enthusiasts would memorialize the sleeve-valve engine with home-built models and on Web sites in the decades to follow. Some flying model planes use miniature sleeve-valve engines. And it's conceivable the technology could experience a resurgence in some of the world's largest and fastest-growing automotive markets.